/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    ManhattanDistance.java
 *    Copyright (C) 2007-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.core;

import weka.core.TechnicalInformation.Field;
import weka.core.TechnicalInformation.Type;

/**
 * <!-- globalinfo-start --> Implements the Manhattan distance (or Taxicab
 * geometry). The distance between two points is the sum of the (absolute)
 * differences of their coordinates.<br/>
 * <br/>
 * For more information, see:<br/>
 * <br/>
 * Wikipedia. Taxicab geometry. URL
 * http://en.wikipedia.org/wiki/Taxicab_geometry.
 * <p/>
 * <!-- globalinfo-end -->
 *
 * <!-- technical-bibtex-start --> BibTeX:
 * 
 * <pre>
 * &#64;misc{missing_id,
 *    author = {Wikipedia},
 *    title = {Taxicab geometry},
 *    URL = {http://en.wikipedia.org/wiki/Taxicab_geometry}
 * }
 * </pre>
 * <p/>
 * <!-- technical-bibtex-end -->
 *
 * <!-- options-start --> Valid options are:
 * <p/>
 * 
 * <pre>
 *  -D
 *  Turns off the normalization of attribute 
 *  values in distance calculation.
 * </pre>
 * 
 * <pre>
 *  -R &lt;col1,col2-col4,...&gt;
 *  Specifies list of columns to used in the calculation of the 
 *  distance. 'first' and 'last' are valid indices.
 *  (default: first-last)
 * </pre>
 * 
 * <pre>
 *  -V
 *  Invert matching sense of column indices.
 * </pre>
 * 
 * <!-- options-end -->
 *
 * @author Fracpete (fracpete at waikato dot ac dot nz)
 * @version $Revision$
 */
public class ManhattanDistance extends NormalizableDistance implements TechnicalInformationHandler {

    /** for serialization. */
    private static final long serialVersionUID = 6783782554224000243L;

    /**
     * Constructs an Manhattan Distance object, Instances must be still set.
     */
    public ManhattanDistance() {
        super();
    }

    /**
     * Constructs an Manhattan Distance object and automatically initializes the
     * ranges.
     * 
     * @param data the instances the distance function should work on
     */
    public ManhattanDistance(Instances data) {
        super(data);
    }

    /**
     * Returns a string describing this object.
     * 
     * @return a description of the evaluator suitable for displaying in the
     *         explorer/experimenter gui
     */
    public String globalInfo() {
        return "Implements the Manhattan distance (or Taxicab geometry). The distance " + "between two points is the sum of the (absolute) differences of their " + "coordinates.\n\n" + "For more information, see:\n\n" + getTechnicalInformation().toString();
    }

    /**
     * Returns an instance of a TechnicalInformation object, containing detailed
     * information about the technical background of this class, e.g., paper
     * reference or book this class is based on.
     * 
     * @return the technical information about this class
     */
    public TechnicalInformation getTechnicalInformation() {
        TechnicalInformation result;

        result = new TechnicalInformation(Type.MISC);
        result.setValue(Field.AUTHOR, "Wikipedia");
        result.setValue(Field.TITLE, "Taxicab geometry");
        result.setValue(Field.URL, "http://en.wikipedia.org/wiki/Taxicab_geometry");

        return result;
    }

    /**
     * Updates the current distance calculated so far with the new difference
     * between two attributes. The difference between the attributes was calculated
     * with the difference(int,double,double) method.
     * 
     * @param currDist the current distance calculated so far
     * @param diff     the difference between two new attributes
     * @return the update distance
     * @see #difference(int, double, double)
     */
    protected double updateDistance(double currDist, double diff) {
        double result;

        result = currDist;
        result += Math.abs(diff);

        return result;
    }

}
